Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), so the description's job is to add context—and it does, disclosing the edge fallback behavior (BR with source: "fallback") and the meaning of the `detected` field. It still says nothing about caching semantics or how long a suggestion stays valid, but the added operational detail is genuinely useful.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Two tight sentences with the core purpose front-loaded and the edge-case behavior second. The opening clause is a mild restatement of the title, but no sentence is wasted.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With no output schema, the description carries the burden of describing return values, and it only documents `source` and `detected` indirectly. The likely companion fields (the country and language values themselves) are never named, so an agent knows the fallback story but not the full response shape.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The tool takes no parameters (0 required, 0 properties), so the baseline is 4. Nothing in the description contradicts or muddies that, and there is no parameter meaning left to explain.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description states the resource it returns—the country and language suggested for the caller—and explains the fallback case, so an agent understands this is a zero-arg geo resolver rather than a listing tool. It does not explicitly distinguish itself from siblings like list_countries or list_languages, leaving some ambiguity about which geo tool to pick.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Usage is only implied: the phrase 'suggested for the caller' suggests this is for resolving the caller's own geo context. There is no explicit when-to-use statement, no preconditions, and no routing guidance naming list_countries/list_languages as the alternatives for enumeration.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.